Currently, bulk polycrystalline varistors are generally used for high voltage circuit protection, while low voltage and ultra-low voltage protection has been a less-touched area without a true analogue product to the high voltage surge arrestor. The general processing methods of prior art varistors typically involve bulk approaches, for example, a polycrystalline sintering process. Such bulk processing does not allow for precise controllability of the various fabrication steps. Furthermore, prior art varistors also lack controllability during operation. Currently, the operating points (e.g., breakdown voltage) of varistors are not capable of being modulated.